In prior art, its holder has a torque-setting mechanism inside, which is triggered through an torque-adjusting button that can move the operational bar vertically to depress or stretch the spring set between supporting ring and torque-adjusting nut. However, the mechanism between the clutch and the torque-adjusting button is weak, so the operational bar, clutch, spring, and the torque-adjusting nut would move synchronously when the torque-adjusting button is turned, making it unable to use.